The M.O. is exactly like you described.

The pump won't run when the car is not in use.

The leak in the rubber spring is rarely fast enough the pump will run much. Usually if that happens it's a pipe leak. (though it can be a catastrophic failure in the spring).

If you remove the wheel, jack up the car (other order I suppose is important). Then spray some spray cleaner on the rubber spring. If you see foam you've confirmed the leak.

Of the 20-25 cases I've witnessed on xo, 2 perhaps were not the spring so that's the way to bet.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)